New graphics,but question regarding power supply

Hello friends, in the coming week i am upgrading my computer with a new graphic card, ram and hopefully Cpu(if comes in the budget).
My question is regarding my PSU if it poweful enough For all of the new specs.

Firstly old configuation:
Cpu :Intel Dual core E2140 @1.6Ghz(oc to 2.1 GHz)
Mobo:Intel G43 express Chipset(dont know the brand nothing written on it)
Ram:1Gb ddr2 667 mhz
Hdd:WD 320 gb
Gpu:---
PSu:CIL-PDYSSEY oct 2008 450 w(as written on it,dont think its good enough)

New Specs :
Cpu:Intel Core 2 Duo E8400 3.0 GhzOr Core 2 Quad Q8300 2.5 Ghz
Mobo:same-Intel G43 express Chipset
Ram:4GB DDR2 800 mhz
Gpu:Ati radeon 5670 512MB GDDR5
PSU:same or if required New (want some suggestions)

I used to play games like Far Cry 2 with old specs with 15-20 fps.But sometimes(often many times) games suddenly freezes and the computer restars.Is it because of the PSU or something else.This happens even in games like Halo1.
I forgot to mention the frequency of ram goes up to 834 Mhz.
I want your expertise regarding the issues.